Many electronic devices are powered by batteries. Rechargeable batteries are often used to avoid the cost of replacing conventional dry-cell batteries and to conserve precious resources. However, recharging batteries with conventional rechargeable battery chargers requires access to an alternating current (AC) power outlet, which is sometimes not available or not convenient. It would, therefore, be desirable to access battery recharging power for electronic devices wirelessly.
In the field of wireless charging, safe and reliable use within a business or home environment is of the utmost concern. To date, wireless charging has been limited to magnetic or inductive charging based solutions. Unfortunately, these solutions require a wireless power charging transmission system and a receiver to be in relatively close proximity to one another. Wireless power transmission at larger distances requires more advanced mechanisms such as, for example, transmission via radio frequency (RF) signals, ultrasonic transmissions, laser powering, to name a few, each of which presents a number of unique hurdles to commercial success.
The most viable systems to date utilize power transmission via RF. However, in the context of RF transmission within a residence, commercial building, or other habited environment, there are many reasons to limit the RF exposure levels of the transmitted signals. Consequently, power delivery is constrained to relatively low power levels (typically on the order of milliwatts (mW)). Due to this low energy transfer rate, it is imperative that the system is efficient.
In a free-space wireless environment, radiation from an omnidirectional radiator or antenna propagates as an expanding sphere. The power density is reduced as the surface area of the sphere increases in the ratio of 1/r2, where r is the radius of the sphere. This type of radiator is often referred to as isotropic, normally has an omnidirectional radiation pattern, and it is usually referred to in antenna terms as directivity vs. gain (dBi—decibels over isotropic). If the intended receiver of the transmission is at a particular point relative to the transmitting radiator, being able to direct the power toward an intended receiver means that more transmission power will be available at the receiving system for a given distance than would have been the case if the power had been omnidirectional radiated. This concept of directivity is very important because it improves the system performance. A very simple analog is seen in the use of a small lamp to provide light and the effect of directing the light energy using a reflector or lens to make a flashlight where the light energy is used to illuminate a preferred region at the expense of having little to no illumination elsewhere.
Central to mechanisms for directionally focusing transmissions in charging-over-the-air (COTA) systems is the ability to receive wireless transmitted power and to either use the power immediately or to store it for later use. There are many battery-powered devices having internal rechargeable batteries that rely on corded connections with power sources to operate or to receive charging power to replenish spent battery energy. These legacy devices are not typically capable of being retrofitted with COTA technology to eliminate the need for receiving recharging power via attached cords.
Retro-directive array systems (or any wireless system that operates based of the reception, processing and transmission) typically rely on frequent incoming signals in order to track moving clients. A reliable reception during the beaconing cycle is important for phase measurements, although such reliable reception is not always achievable. This can be due to substantial or partial blockage of signals, noise, in-band interference, and poor receptions in general.
Accordingly, a need exists for technology that overcomes the problem demonstrated above. The examples provided herein of some prior or related systems and their associated limitations are intended to be illustrative and not exclusive. Other limitations of existing or prior systems will become apparent to those of skill in the art upon reading the following Detailed Description.
Overview
In one example, a predictive phase estimation apparatus comprises a transceiver module configured to receive a plurality of beaconing signals from a wireless client during a beacon cycle. The wireless client moves from a first position to a second position. The predictive phase estimation apparatus also comprises a phase compensation module configured to store the received plurality of beaconing signals, a phase predictor module is coupled to the transceiver module and configured to calculate predictive phases based on the received plurality of beaconing signals and based on beaconing signals received from the wireless client prior to the beacon cycle, and a signal converter coupled to the transceiver module. The signal converter is configured to form transmission signals based on the predictive phases and supply the transmission signals to the transceiver module. The transceiver module is further configured to transmit the transmission signals for delivery of wireless power to the wireless client.
In another example, a predictive phase estimation system comprises a master bus controller (MBC) board that comprises a transceiver configured to receive a plurality of beaconing signals from a wireless client during a beacon cycle, a phase compensator configured to store the received plurality of beaconing signals, and a phase predictor coupled to the transceiver and configured to calculate predictive phases based on the received plurality of beaconing signals and based on beaconing signals received from the wireless client prior to the beacon cycle. The MBC board also comprises a signal converter coupled to the transceiver and configured to form transmission signals based on the predictive phases and supply the transmission signals to the transceiver. The transceiver is further configured to transmit the transmission signals for delivery of wireless power to the wireless client.
In another example, a method of predictive phase estimation comprises receiving, by a transceiver, a plurality of beaconing signals from a wireless client during a beacon cycle, storing the received plurality of beaconing signals, and calculating predictive phases based on the received plurality of beaconing signals and based on beaconing signals received from the wireless client prior to the beacon cycle. The method also comprises forming transmission signals based on the predictive phases, supplying the transmission signals to the transceiver and transmitting the transmission signals for delivery of wireless power to the wireless client. The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.